Testing a system for vulnerabilities is the best way to ensure that the system is, oris not, vulnerable to a particular problem.Vulnerability testing is a necessary andmandatory task for anybody involved with the administration or security ofinformation systems.You can only ensure system security by attempting to breakinto your own systems.Up to this point, we have discussed the different types of vulnerabilities thatmay be used to exploit a system. In this section, we discuss the methods offinding and proving that vulnerabilities exist, including exploit code.We also discusssome of the methods used in gathering information prior to launching anattack on a system, such as the use of Nmap.